Hi

I'm studying for the SCJP 5.0 and have a question about Generic
Collections.

The question is, If I use wildcards in a collection then I can't use
the add() method for the collection (ArrayList in this example). I can
use a wildcarded ArrayList to asign other ArrayLists to this but what
is the big purpose of this?

Can anybody explain that to me, help would be very apreciated.

-------------------------- Code Example --------------------------
import java.util.*;
public class AnimalGenericTester {

 public AnimalGenericTester() {
   ArrayList<Animal> myList = new ArrayList<Animal>();
   myList.add(new Dog());
   myList.add(new Cat());
   printAnimal(myList);
 }

 void printAnimal(ArrayList<? super Cat> list) {
   //What is the purpose of this???
   //The myList now contains a Dog and a Cat but Dog is NOT a super of
cat
   //I really can't see the point of this generic functionality
 }

 public static void main(String[] args) {
   new AnimalGenericTester();
 }

}

abstract class Animal {
 abstract void checkup();

}

class Dog extends Animal {
 void checkup() {
   System.out.println("Dog");
 }

}

class Cat extends Animal {
 void checkup() {
   System.out.println("Cat");
 }

}

-------------------------- END OF Code Example
--------------------------